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                            <h1 itemprop="headline" class="wsf-worksheet-title">
				Dandelin's theorem				</h1>
            

                            <p class="bbcode-text" itemprop="articleBody">* Move points A and B to change section of the cone
* Spheres are tangent to the plane and to the cone
* Move point P on the conic
* When the conic is an ellipse, why is MP+PH constant ?</p>
            
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